This project has as its basic goal an understanding of the structure and behavior of the mammalian erythrocyte membrane. Major effort has centered attention on those factors contributing to the stability of the plasma membrane and how this may interrelate to the age of the erythrocyte. One particular direction of the work now is towards evaluating the importance of an activator of the Ca2/Mg2 ions ATPase in the human erythrocyte. This small molecular weight protein is released upon hemolysis of the red cells at pH 7.6 and can be shown to have significant influence on the ATPase activity in these membranes. Efforts are being explored to see whether this protein might be involved in stabilizing the red cell membrane in the presence of calcium ion. In addition, human erythrocytes and other species of erythrocytes are being separated by a density centrifugation method devised by Dr. Murphy at Case Western Reserve (Cleveland). An examination of the various (separated) age group cells will be undertaken and the nature of the membranes obtained from each group will be explored. In particular, a search for the factors most important in their aging will be made and the conformation and orientation of lipids in these membranes will be investigated. In the latter instance it will be important to ascertain whether the membrane lipids undergo a reorientation or conformational change during the aging process and also during the preparation of membranes.